1. Field of the Invention
This invention relates to reproduction apparatus in general and, more specifically, to copier/duplicators or the like. More particularly, the invention relates to the structure and control of a copier/duplicator so that two documents can be selectively copied.
2. Description of the Prior Art
Copier/duplicators typically comprise a single platen against which an original document is positioned for copying by exposing the document while on the platen and projecting an image of the document onto a photoconductor where the image is developed. The image then is transferred to a copy sheet and fused to the copy sheet. It is also known to provide document feeders which repetitively feed sheets of a multi-sheet document from a stack to the platen and then away from the platen so that the copier produces collated sets of copies. Examples of such document feeders are disclosed in the before mentioned copending U.S. patent application and in U.S. Pat. No. RE 27,976. Recirculating document feeders as disclosed in such copending application, provide significant improvements in the copying operation, especially in regard to the convenience to the user and the ability to make sets of copies without the need for a collator. However, when a user wishes to make copies of an especially large original document, or when the original document is prepared by pasting or otherwise assembling various portions of the document onto a backing sheet, the original may not feed reliably through the recirculating feeder. In some cases the recirculating feeder can be swung away from the platen to place the original document onto the platen, and then one or more copies of the original can be made. One or more "master" copies can be made in this manner and then placed in the recirculating feeder in order to produce collated sets of copies. However, it is somewhat inconvenient to move the recirculating feeder away from the platen, and it clearly would be advantageous to be able to make copies from oversize originals, paste-up documents or from other documents without having to manually interrupt the job being run on the recirculating feeder, swing the feeder away from the platen, make the required number of copies of the over-size or paste-up originals, and then restart the recirculating feeder operation. Also, when a long job is being run on a copier, it is desireable to be able to interrupt that job and run a short job or one with a higher priority with a minimum of inconvenience to the operator.
In some instances apparatus have been provided for making masters in a separate part of the copying apparatus and then feeding the master onto a cylinder or the like where a multitude of copies are made from the master in the usual manner. For example, see Canadian Pat. No. 946,460. This patent also discloses the idea of concurrently processing a master while copies are being made from a preceding master, and for delaying preparations of the second master until the printing time remaining in the printing run from the first master is about equal to the time required to make the second master. Other apparatus of this general type are disclosed in U.S. Pat. Nos. 3,612,682; 3,754,820; 3,827,803; 3,861,306 and 3,390,634. In addition, apparatus for making masters by means of an electrophotographic process are disclosed in a number of patents, including U.S. Pat. Nos. 3,448,970; 3,498,712 and 3,504,973